Mixtures Of Metal Salts Research Articles

Efficient conversion of xylose and corncob to furfural using a novel carbon-based solid acid derived from black liquor lignin-tin complexes

The novel carbon-based solid acid catalyst was prepared by carbonizing the mixture of metal salts and black liquor, followed by sulfonating. The physicochemical properties of the catalysts were characterized by SEM, FTIR, BET, NH3-TPD, Py-IR, XPS, ICP, and elemental analysis. The catalytic ability of the catalyst was explored by converting xylose and corncob to furfural via a one-step process. The effects of solvent types and water contents, catalyst dosage, substrate concentration, reaction temperature, and reaction time on furfural yield were evaluated. 93.4 % of furfural yield was achieved using 200 mg xylose at 170 °C for 120 min with 150 mg catalysts. Moreover, the furfural yields of 82.5 % were obtained from corncob. This work provides a promising strategy for synthesizing carbon-based solid acid catalysts from pulp waste black-liquid resources, which has a potential application for producing furfural from hemicellulose.

In-Depth Analysis of the Species and Transformations during Sol Gel-Assisted V2PC Synthesis.

The sol-gel reaction mechanism of 211 MAX phases has proven to be very complex when identifying the intermediate species, chemical processes, and conversions that occur from a mixture of metal salts and gelling agent into a crystalline ternary carbide. With mostly qualitative results in the literature (Cr2GaC, Cr2GeC, and V2GeC), additional analytical techniques, including thermal analysis, powder diffraction, total scattering, and various spectroscopic methods, are necessary to unravel the identity of the chemical compounds and transformations during the reaction. Here, we demonstrate the combination of these techniques to understand the details of the sol-gel synthesis of MAX phase V2PC. The metal phosphate complexes, as well as amorphous/nanocrystalline vanadium phosphate species (V in different oxidation states), are identified at all stages of the reaction and a full schematic of the reaction process is suggested. The early amorphous vanadium species undergo multiple changes of oxidation states while organic species decompose releasing a variety of small molecule gases. Amorphous oxides, analogous to [NH4][VO2][HPO4], V2PO4O, and VO2P2O7 are identified in the dried gel obtained during the early stages of the heating process (300 and 600 °C), respectively. They are carbothermally reduced starting at 900 °C and subsequently react to crystalline V2PC with the excess carbon in the reaction mixture. Through CHN analysis, we obtain an estimate of left-over amorphous carbon in the product which will guide future efforts of minimizing the amount of carbon in sol gel-produced MAX phases which is important for subsequent property studies.

In situ Investigations of the Formation Mechanism of Metastable γ-BiPd Nanoparticles in Polyol Reductions.

Synthesizing intermetallic phases containing noble metals often poses a challenge as the melting points of noble metals often exceed the boiling point of bismuth (1560 °C). Reactions in the solid state generally circumvent this issue but are extremely time consuming. A convenient method to overcome these obstacles is the co-reduction of metal salts in polyols, which can be performed within hours at moderate temperatures and even allows access to metastable phases. However, little attention has been paid to the formation mechanisms of intermetallic particles in polyol reductions. Identifying crucial reaction parameters and finding patterns are key factors to enable targeted syntheses and product design. Here, we chose metastable γ-BiPd as an example to investigate the formation mechanism from mixtures of metal salts in ethylene glycol and to determine critical factors for phase formation. The reaction was also monitored by in situ X-ray diffraction using synchrotron radiation. Products, intermediates and solutions were characterized by (in situ) X-ray diffraction, electron microscopy, and UV-Vis spectroscopy. In the first step of the reaction, elemental palladium precipitates. Increasing temperature induces the reduction of bismuth cations and the subsequent rapid incorporation of bismuth into the palladium cores, yielding the γ-BiPd phase.

N-Doped carbon nanotubes encapsulated FeNi alloy in persulfate activation for nonradical Reaction: Confined metal redox

A heterophane FeNi alloy confined in N-doped carbon nanotubes (FeNi-NC) catalyst was fabricated via pyrolysis of a mixture of metal salts and N/C precursors under inert conditions. The as-synthesized FeNi-NC was functionalized as heterogeneous Fenton-like catalysts for elimination of aqueous organic contaminants via potassium peroxydisulfate (PDS) activation. The effects of carbonization temperatures and Ni/Fe atomic ratios on the structure of FeNi-NC and catalytic properties were investigated. Benefiting from the designed structure and highly exposed active sites, the FeNi-NC catalyst manifests excellent catalytic activities and durability, better than those of the corresponding monometallic catalysts. Electron paramagnetic resonance and radical quenching tests indicated that the typical nonradical-involved (i.e., mediated electron transfer and singlet oxygenation) catalytic process occurred during the PDS activation. The interaction between PDS and FeNi-NC could be boosted by inner FeNi redox process and thus accelerated the electron transfer between PDS and carbon layer due to confined effect, resulting in dramatically enhanced performance. The Fe species in the alloy can improve the charge transfer for the effective reduction of Ni3+ to Ni2+ and inhibit the generation of unwanted Ni component with a high oxidation state. This work offers new insights to non-precious-metal alloy catalysts toward highly efficient wastewater treatment.

(Invited, Digital Presentation) Infiltrated Electrodes for High Temperature Energy Conversion, Electrolysis, and Chemical Synthesis

Solid oxide cell (SOC) infiltrated electrodes typically consist of a ceramic or cermet porous scaffold with the pore walls coated with catalyst particles. The pore size of the scaffold is 1 to 50 mm, whereas the catalyst particles are 10 to 300 nm. This scaffold provides a stable and durable mechanical structure, and the fine catalyst particles provide high surface area for electrochemical and heterogeneous reactions. The scaffold is sintered and bonded to the other layers of the complete cell. After this high temperature processing is finished, catalyst precursor solution is flooded into the scaffold and fired at moderate temperature to form the desired catalyst composition and phase. Because the scaffold is sintered in the absence of catalysts, re-optimization of the fabrication process, ink formulation, deposition process, and sintering protocol is not needed when a new catalyst is introduced to the cell design. Instead, a new precursor solution can be prepared from a stoichiometric mixture of metal salts, with minimal change in processing. This approach makes it straightforward to screen many catalyst compositions in a short period of time, and adapt an existing cell structure for a wide variety of applications.The Lawrence Berkeley National Laboratory metal-supported solid oxide cell (MS-SOC) design has a thin electrode scaffold of zirconia ceramic co-sintered on a thick porous stainless steel support layer. Both layers are coated with infiltrated catalysts. The catalyst precursor solution is an aqueous mixture of metal nitrate salts. After the solution is flooded into the pores of the scaffold, it is dried and heated in air to convert the nitrate salts to mixed metal oxides. The oxides can then be reduced to metals by firing in reducing atmosphere, if desired. The drying rate, heating rate, conversion temperature, and other processing parameters can have a dramatic impact on the catalyst particle morphology and ultimately on the performance and durability of the electrochemical device.Depending on the choice of catalyst composition, the MS-SOCs can be configured as fuel cells, electrolysis cells, or chemical conversion reactors. Several examples will be highlighted, including: fuel cell operation with hydrogen, ethanol, and natural gas; steam electrolysis for hydrogen production; and oxidative coupling of methane for valuable chemical synthesis. In each case, technical progress will be presented with a focus on catalyst development and device performance. Figure 1

Evaluation of biochemical markers in the blood plasma of rats exposed to chronic administration of a mixture of metal nanoparticles

The aim of this study was to determine the effects of a specific mixture of metal nanoparticles (Ag, Cu, Fe and MnО2) orally administered to rats, on biochemical blood markers as indicators of chronic toxicity. Animals (Wistar line rats (n=20)) in experimental groups were given a solution of a mixture of metal salts or a mixture of nanoparticles with food for 90 days. On days 15, 30, 60 and 90 of the experiment, five rats from each group were anaesthetised with CO2 and decapitated, and blood samples were collected for biochemical studies and spectrophotometric measurement. The toxic effect of the chronic administration of the mixture at a dose of 4.0 mg/kg of body weight in white rats caused partial immunosuppression expressed as hypoproteinaemia, excessive formation of circulating immune complexes and acute phase serum mucoid proteins (P<0.05), and cytolytic damage to hepatocyte membranes. Levels of enzyme activity (AST, GGT, ALT and AP) were significantly elevated (P<0.05). It has been shown that the origin of the toxic effect is due to oxidative stress, which slowed lipoperoxidation along with the elevation of the level of carboxylated proteins, depleting the antioxidant defence resources of the organism, as seen by a decrease in the level of catalase and total antioxidant activity (P<0.05). No such effects were observed at the dose of 0.3 mg/kg as there were no significant negative impacts on the biomarkers. Based on this data, the biochemical markers studied may be suitable for use in pre-clinical in vivo toxicological assessment of metal nanoparticle-candidates for pharmaceuticals.

Mononuclear Manganese(IV) Complexes Derived from Polyfunctional Fumaryldihydrazone

A series of mononuclear manganese(IV) complexes of disalicylaldehyde fumaroyldihydrazone (slfhH4) were synthesized by reacting manganese acetate tetrahydrate with dihydrazone in absence and presence of various pyridine bases in methanol medium. Pyridine (py) and its derivatives like 2-picoline (2-pic), 3-picoline (3-pic), 4-picoline (4-pic), 2,2′-bipyridine (bpy) and 1,10-phenanthroline (phen) were added to the reaction mixture of metal salt and dihydrazone to explore the binding possibilities of these molecules to manganese center. The elemental analysis, mass spectral and thermal studies were used to derive their composition. Study of magnetic moment, molar conductances, electronic, EPR and infrared spectroscopy have led to interpretation of their tentative structures. Magnetic moment and EPR studies correspond to their Mn(IV) oxidation state. The dihydrazone functions as tetradentate ligand chelating the manganese(IV) ion present in octahedral geometry with anti-cis configuration in enol form. Electrochemical and antimicrobial studies were also performed.

Effects of natural organic matter on the joint toxicity and accumulation of Cu nanoparticles and ZnO nanoparticles in Daphnia magna

Various modern products have metallic nanoparticles (MNPs) embedded to enhance products performance. Technological advances enable nowadays even multiple hybrid nanoparticles. Consequently, the future co-release of multiple MNPs will inevitably result in the presence of MNP mixtures in the environment. An important question is if the responses of mixtures of MNPs can be dealt with in a similar way as with the responses of biota to mixtures of metal salts. Moreover, natural organic matter (NOM) is an important parameter affecting the behavior and effect of MNPs. Herein, we determined the joint toxicity and accumulation of copper nanoparticles (CuNPs) and zinc oxide nanoparticles (ZnONPs) in Daphnia magna in the absence and presence of Suwannee River natural organic matter (SR-NOM), compared to the joint toxicity and accumulation of corresponding metal salts. The results of toxicity testing showed that the joint toxicity of CuNPs + ZnONPs was greater than the single toxicity of CuNPs or ZnONPs. The joint toxic action of CuNPs + ZnONPs was additive or more-than-additive for D. magna. A similar pattern was found in the toxicity of the mixtures of Cu- and Zn-salts from the literature data. The presence of SR-NOM had no significant impact on the joint toxicity of CuNPs + ZnONPs. The calculated component-specific contribution to overall toxicity indicated that SR-NOM increased the relative contribution of dissolved ions released from the MNPs to the toxicity of the binary mixtures at high-effect concentrations of individual MNPs. Moreover, dissolved Zn-ions released from the ZnONPs were found to dominate the joint toxicity of CuNPs + ZnONPs in the presence of SR-NOM. Furthermore, the results of the accumulation experiment displayed that the presence of SR-NOM significantly enhanced the accumulation of either CuNPs or ZnONPs in D. magna exposed to the MNP mixtures.

The Impact of Nickel Content on Structure and Electrochemical CO2 Reduction Performance of Nickel-Nitrogen-Carbon Catalysts Driven By Zeolitic Imidazolate Frameworks As a Platform

The electrochemical conversion of CO2 to chemicals and fuels is a promising strategy to overcome the increase of CO2 concentration in the atmosphere driven by the extensive dependence on fossil fuels as a main global energy source. A significant shortcoming of this technology is the ability to design new active and selective catalysts for CO2reduction (CO2R) reaction. Atomically dispersed metal-nitrogen doped carbon (M-N-C) materials has attracted extensive attention as highly selective and active electrocatalysts for CO2R due to their exceptional geometric structures and electronic properties compared to other materials. M-N-C electrocatalysts are being synthesized by simple chemical methods through pyrolyzing a mixture of metal salt, nitrogen and carbon containing precursors. Among different precursors, metal organic frameworks (MOFs) are being widely used as a platform for driving M-N-C catalysts owing to their well-defined structures that can assist in forming and isolating the atomically dispersed metal sites doped in N-C skeleton. While several M-N-C (where M=Fe, Co, Mn, Ni) catalysts were utilized for CO2R, atomically dispersed Ni-Nx sites were found to be very selective for the CO2R towards CO. However, the influence of the metal concentration impregnated into the prepared structure on the overall performance of M-N-C catalysts in CO2R is still under investigation.Herein, we’ve selected zeolitic imidazolate frameworks (ZIF-8) — a subclass of MOFs — as a platform for synthesizing Ni-N-C electrocatalyst. A systematic study has been performed to investigate the role of Ni concentration integrated into the structure of ZIF-8 during the synthesis on the structure, properties and overall CO2R activity and selectivity of the prepared Ni-N-C catalyst. A series of four Ni concentrations has been investigated in CO2electroreduction system, our findings exhibit that higher Ni impregnation concentration has resulted in forming metallic Ni nanoparticles which are favouring the competing hydrogen evolution reaction (HER), while low Ni content has assisted on the formation of atomically dispersed and isolated Ni active sites which are very selective towards CO in CO2R ~99% Faradaic efficiency at a potential of -0.68 V vs the reversible hydrogen electrode. Through this study, we show how the optimization of the Ni content in the prepared Ni-N-C catalysts has a significant impact on their performance as CO2R electrocatalysts.

The co-occurrence of Zn-and Cu-based engineered nanoparticles in soils: The metal extractability vs. toxicity to Folsomia candida

The presence of engineered nanoparticles (ENPs) in soil gradually increases, among others due to the nano-agrochemicals application. So far, the co-existence of different ENPs in soil is poorly examined. Here, the metal extractability and toxicity of soils spiked (300 mg kg−1) singly and jointly with Zn- and Cu-based ENPs or metal salts were tested. The samples were aged for 1 and 90 days. The predicting available metal component of ENPs concentrations were determined by different methods including soil pore water collection and batch extractions with H2O, CaCl2 or DTPA. Survival and reproduction of Folsomia candida were also evaluated. The combined effect of ENPs on the extractability of metals was mainly found with DTPA characterized by the highest leaching capacity among the used extractants. In fresh soil, the mixtures of ENPs differentiated only DTPA-extractable Cu level, while aging resulted in changes in both Zn and Cu concentrations leached by CaCl2 or DTPA. However, the character of the combined effect was an ENPs- and soil type-dependent, whereas the mixtures of metal salts mostly provided higher Zn and Cu recovery than the individual compounds. The pattern of co-toxicity of metal-oxide ENPs was also time-dependent: the antagonistic and synergistic effect was observed in the samples after 1 and 90 days, respectively. However, the toxicity was weakly related with extractable concentrations in both single and joint treatment of metal compounds. The distinct joint effect patterns of ENPs imply the need for more in-depth investigation of mechanisms of activity of ENPs mixtures in soil.

Increasing exposure of atomically dispersed Ni sites via constructing hierarchically porous supports for enhanced electrochemical CO2 reduction

Atomically dispersed metal catalysts have been widely utilized for electrocatalysis, such as the electrochemical reduction of CO2, due to their low coordination number and maximum utilization of metal active sites. However, it remains a major challenge to develop an effective and convenient strategy for fully exposing the active sites of atomically dispersed metal catalysts within supports. Herein, we describe an operationally simple and sustainable strategy for preparing hierarchically porous thin-wall carbon networks with highly exposed atomically dispersed Ni sites by directly pyrolyzing a ground mixture of metal salts and organic ligands. Compared with the preformed metal organic framework-derived materials, the amount of exposed active Ni sites can be increased by ~50% for hierarchically porous materials. The hierarchically porous atomically dispersed Ni electrocatalyst shows obviously enhanced CO2RR catalytic performance with higher CO Faradaic efficiency (over 99% at −0.88 V) and high TOF value of 7025 h−1 (72.6% higher than that for the metal organic framework-derived materials). The excellent activity can be attributed to the increased exposure of atomically dispersed Ni sites with hierarchically porous structure and interconnected thin-wall carbon networks, which ensure the fully exposure of electrocatalytically active sites and promotion of mass transport and electron transfer. Density functional theory calculations further suggest that the fully exposed Ni sites are responsible for highly efficient activation of CO2 rather than the carbon layer-covered Ni sites.

FeNi Alloy Nanoparticles Encapsulated in Carbon Shells Supported on N-Doped Graphene-Like Carbon as Efficient and Stable Bifunctional Oxygen Electrocatalysts.

The development of cost-effective and durable oxygen electrocatalysts remains highly critical but challenging for energy conversion and storage devices. Herein, a novel FeNi alloy nanoparticle core encapsulated in carbon shells supported on a N-enriched graphene-like carbon matrix (denoted as FeNi@C/NG) was constructed by facile pyrolyzing the mixture of metal salts, glucose, and dicyandiamide. The in situ pyrolysis of dicyandiamide in the presence of glucose plays a significant effect on the fabrication of the porous FeNi@C/NG with a high content of doped N and large specific surface area. The optimized FeNi@C/NG catalyst displays not only a superior catalytic performance for the oxygen reduction reaction (ORR, with an onset potential of 1.0 V and half-wave potential of 0.84 V) and oxygen evolution reaction (OER, the potential at 10 mA cm-2 is 1.66 V) simultaneously in alkaline, but also outstanding long-term cycling durability. The excellent bifunctional ORR/OER electrocatalytic performance is ascribed to the synergism of the carbon shell and FeNi alloy core together with the high-content of nitrogen doped on the large specific surface area graphene-like carbon.

Transovarial effect of the mixture of metal nanoparticles (Ag, Cu, Fe, MnO2) on biochemical indices of blood of one-day-old chickens compared to metal salts

Aim. Due to small sizes of metal nanoparticles (NPMe), after getting into the organism, they penetrate different internal organs, overcoming hematoencephalitic and placental barriers, and may cause different pathophysiological effects in the organism. Thus, the aim of our study was to study transovarial effect of NPMe mixture (Ag, Cu, Fe, MnO2 ) on biochemical indices of blood of one-day-old chickens compared to salts of relevant metals. Methods. The studies were conducted using Hisex White cross chickens (n = 28) with the sex ratio of roosters to hens of 1:6, which were fed for 37 days with the following additives: an experimental sample of NPМе mixture, containing nanoparticles of silver (31.5 ± 0.9 nm), iron (100.0 ± 10.0 nm), copper (70.0 ± 4.0 nm) and manganese peroxidase (50.0 ± 3.0 nm), in the doses of 0.3 and 4.0 mg/kg of bodyweight (experiments ІІ and ІІІ); solution of salt mixture – AgNO3 , (CuSO4 ∙ 5H2 O), (MnSO4 ∙ 5H2 O) and (FeSO4 ∙ 7H2 O) (experiment І); distilled water (control). Starting with Day 30 of the experiment, eggs were collected from poultry in each group for a week and placed for further incubation. Blood samples were taken from hatched one-day-old chickens (n = 93) for biochemical studies. The registration of biochemical indices was conducted using spectrophotometer SHIMADZU UV-1800 (Japan). Results. The experiments determined the mechanism of toxic effect of NPMe mixture after its administration to chickens in the dose of 4.0 mg/kg of bodyweight, which was manifested in decreasing the natural resistance (tendency to the increase in seromucoids – immunosuppressive proteins), excessive formation of toxic products of purine exchange (increase in the concentration of uric acid by 77.6 %; P < 0.05) and straining of enzyme systems of natural detoxication (increase in the activity of alanine aminotransferase and aspartate aminotransferase by 23.8 and 31.6 %; P < 0.05) with the development of oxidative stress (increase in the content of diene conjugates and malondialdehyde by 19.3 and 23.8 %; P < 0.01) in the organism of one-day-old chickens. The mechanism of pharmacological effect of NPMe mixture at its administration to chickens in the dose of 0.3 mg/kg of bodyweight lies in enhancing immune reactions (increasing the amount of general proteins and globulins by 14.4 and 12.0 %; P < 0.05) along with the antioxidant effect via the release of vitamins A and E from the endogenous depot (by 14.7 and 25.7 % above the control; P < 0.05) in the organism of one-day-old chickens. Conclusions. In conditions of transovarial transmission, there is confi rmed advantage of the effect of NPMe mixture (Ag, Cu, Fe, MnO2 ) in the dose of 0.3 mg/kg of bodyweight of laying hens comparing to the effect of the analogue in the form of the mixture of metal salts, which may help in achieving a high percentage of liveability of young birds, forming defensive reactions in the organism of chickens and ensuring full realization of genetic potential in terms of meat or egg productivity of agricultural poultry. The mechanism of toxic effect of metal nanoparticles in the dose of 4.0 mg/kg of bodyweight was determined which will allow elaborating safe regulations for the application of non-organic nanomaterials in modern poultry breeding and timely management of the risks of their application.

Copper–Carbon: An Efficient Catalyst for Oxygen Reduction

A simple and efficient method was developed to prepare a copper–carbon (Cu–C) catalyst with high oxygen reduction reaction (ORR) activity via direct pyrolysis of a mixture of metal salts (Cu(NO3)2·...

Preparing copper doped carbon nitride from melamine templated crystalline copper chloride for Fenton-like catalysis

Heterogeneous catalysts prepared by doping metal ions in g-C3N4 have been demonstrated as a type of promising alternative to the traditional homogeneous Fenton catalysts. The metal–Nx active sites of metal doped g-C3N4 composites are responsible for their enhanced catalytic activity. However, it is very difficult to achieve high content of metal–Nx species through pyrolyzing the physical mixtures of metal salts and g-C3N4 or melamine. In this work, copper doped g-C3N4 composites were synthesized by pyrolyzing a melamine templated crystalline copper chloride [H2mela]2[CuCl5]Cl. High content of Cu–Nx species were formed in these Cu-g-C3N4 composites. Compared with the catalysts prepared by pyrolyzing the physical mixtures of CuCl2 and g-C3N4/mela, the Cu-g-C3N4 composites exhibited enhanced catalytic activities for the degradation of RhB, MO, and MB. This work suggests that crystalline metal chlorides contained melamine ligands could be employed as efficient precursors for synthesizing metal doped g-C3N4 composites with high content of metal-Nx species.

Liquid range of ionic liquid – Metal salt mixtures for electrochemical applications

The effect of the nitrate salt addition on the liquid range of the protic ionic liquid ethylammonium nitrate (EAN) was studied in this work. The salts used were monovalent, LiNO3; divalent, Mg(NO3)2 and Ca(NO3)2, and trivalent, Al(NO3)3; inorganic salts containing metals relevant for electrochemical applications. Solid-liquid transitions, which define the lower limit of the liquid range of the fluids, were determined using differential scanning calorimetry (DSC), whereas the upper limit, which is given by degradation or boiling temperatures, was determined by means of thermogravimetric analysis (TGA). Our results show that salt addition induces melting-point depressions, but no significant boiling point elevations were detected. The so-called nanostructured solvation mechanism is used in order to rationalize the thermodynamics of the mixtures in terms of the occurrence of highly incompressible, low mobility solvation complexes [M(NO3)n]z+−n in the polar cavities of the IL giving rise to pseudo-lattice nanocrystals that are stable in the liquid phase.

Optimisation of electrolytic solvents for simultaneous electrochemical exfoliation and functionalisation of graphene with metal nanostructures

The development of a simple, simultaneous electrochemical exfoliation and functionalisation of graphene with metal nanostructures in a one-pot, single step process is reported. This approach is useful in terms of the reduction in processing time and cost, as well as aiding the control of the aggregation of graphene sheets. This first part of this work compares the efficiency of electrochemical graphite exfoliation in dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP) and in a mixture of dimethyl carbonate (DMC) and ethylene carbonate (EC) in an electrolyte consisting of LiClO4 and tetraethylammonium tetrafluoroborate. In the second part, the best performing electrolytic solvent was used for in-situ functionalisation of graphene sheets with gold or cobalt nanostructures. The formation of solid layer electrolyte interface in the DMC/EC system is believed to stabilise the graphite from premature exfoliation and allowed the ions to intercalate efficiently to produce a relatively high yield of monolayer graphene sheets. By contrast, the electrochemical exfoliation of graphite in the other two solvents (DMSO and NMP) produced lower yields of few layer graphene. In particular, the co-intercalation of DMSO fragments the electrode by its decomposition by-products (sulfur/carbon oxides) before sufficient cation intercalation occurs. The simulations electrochemical exfoliation and functionalisation of graphene at a single applied potential in the presence of Au salt in DMC/EC solution resulted in the functionalisation of graphene sheets with a variety of high surface area Au nanowhiskers, nanodendrites, nanowires and lamellar nanoparticles. Alternatively, the use of Co(II) salt in the exfoliation solution resulted in the co-deposition of uniformly grown Co nanoparticles on graphene sheets. The metal-functionalised graphene sheets showed high catalytic activity and stability when used as an electrocatalyst for hydrogen evolution reactions. This process could be extended to other metal salts, or mixtures of metal salts, to form graphene-metal alloy composites for use in various applications.

Polyol synthesis of ultrathin and high-aspect-ratio Ag nanowires for transparent conductive films

Ultrathin Ag nanowires (AgNWs) with a high aspect ratio of over 1300 were synthesized through NaCl and KBr-mediated polyol reaction. AgNWs became thinner and longer with the increase in NaCl concentration, whereas Ag nanoparticles were formed without NaCl. When 0.4mM of KBr was added, the diameter of the AgNWs decreased further to 20–50nm and its length increased to 30–60µm. The appropriate mixture of metal salts was crucial in synthesizing ultrathin and long AgNWs. Transparent conductive films of AgNWs yielded excellent properties with a sheet electrical resistance of 25Ω/sq and a visible-light transmittance of over 90%.

Leaching of rare earth elements from eudialyte concentrate by suppressing silica gel formation

In this study a two stage hydrometallurgical treatment of eudialyte concentrate is presented, aiming on recovering rare earth elements and suppressing silica gel formation, The proposed treatment incorporates a preprocessing step called “Fuming”, which is the addition of an acidic solution to eudialyte concentrate heated at boiling temperatures, followed by the leaching step, where the treated concentrate is leached at ambient or low temperature. Fuming pretreatment with sulfuric or hydrochloric acid, and subsequently water leaching of the treated concentrate, resulted to >90% recovery of rare earths avoiding silica gel formation which is a major challenge to overcome during eudialyte dissolution. Scanning electron microscopy analysis, indicate that “Fuming”, transforms eudialyte into a mixture of metal salts and a siliceous secondary precipitate. Leaching of the treated concentrate dissolves soluble metal salts into solution whereas the secondary siliceous precipitate remains in the residue with the rest gangue minerals such as aegirine and feldspar. Advantages of the proposed treatment are low acid consumption, high rare earth recovery yields, avoidance of additives such as fluoride ions and avoidance of silica gel formation.

Mg–Al layered double hydroxides modified clay adsorbents for efficient removal of Pb2 +, Cu2 + and Ni2 + from water

Highly effective clay adsorbents of Mg–Al layered double hydroxides modified palygorskite were prepared from the mixture of metal salts, urea and palygorskite by the in situ hydrothermal crystallization method. The obtained adsorbents were characterized by FT-IR, TG, XRD and SEM/EDS. The adsorption performances were evaluated for the removal of Pb2+, Cu2+ and Ni2+ in the aqueous solution. The adsorption capacities of the three metal cations at variable pH, contact times and metal concentrations were determined by atomic adsorption spectrometry. The adsorption capacities of the three metal cations on Mg–Al layered double hydroxides modified palygorskite were higher than those of palygorskite and Mg–Al layered double hydroxides at the initial metal ion concentration of 100mg/L and initial pH of 5.0. The experimental data showed a good compliance with the Langmuir isotherm and the pseudo-second-order kinetic model. Taking advantage of the combined benefits of palygorskite and Mg–Al layered double hydroxides, the as-prepared adsorbents exhibit selective and fast rating adsorption for Pb2+.